Printing-telegraph system



March 24, 1925. 1,539,660

' W. F. FREDMN PRINTING TELEGRA'PH SYSTEM Efilegi July 26. 1922 Uf N Carr/er Wal/e5 /fmf Patented lt/lar. i925..

WILLIAM F. FRIEDMAN, OF W'ASHINGTON, DISTRICT OF ACOLUMIQBIA.'v

PRINTING-TELEGRAPH SlYS'LTlVL` Application Vled July 26T,

To all iii/mm v'zf may concern:

lle it known that l, l/ViLLniii/T F. FRIED- AmN, citizen of the United States` of America, residing at 39.9.() 17th Street NlV., in the city of Washington and District ot lolnmbi-a, have invented certain new and useful Improvements in Printing-Telegraph Systems, of which the Jfollowing is a specilication.

This invention relates to improvements in electrical signaling systems, more particularly to printing telegraph systems, and has for its object the simultaneous transmission and reception of a plurality oi' code signal impulses representing' the individual ele-. ments ol the message characters that are trai'ismitted. i

A further object is ,to reduce very materially the length ot time necessary in the heretofore prevalent printing telegraph systems to transmit the code signals representing the message characters and thus increase the capacity oic the line or channel employed.

A further object is to increasethe number of separate messages which can be transmitted and received simultaneously, thus also increasing the capacity ofthe line or channel employed.

, A further object is to eliminate the -necessity for the employment of synch'ro-nizing mechanisms such vas are required in the heretoli'ore prevalent systems.

The invention will here be illustrated as applied to a Vwell known formel? printing telegraph systems, but, as will be readily understood, is applicable to many other electrical systems and devices Vwhich at present necessitatesthe use of more or less compli-` Lil) cated synchronizing devices.

"lhe fundamental principle oit my inventionfis the-substitution of a plurality of modulated high frequency oscillations of dillerent 'frequencies all transmitted simultaneously and instantaneously for a plurality of similar, equal potential, direct current impulses distributed through time.

lnY the heretoforeylprevalent forms Loit' printing telegraph systems, the automatic operations concerned in causing-a printing mechanism to function at a distance are controlled by groiuiis'ot equal potential, direct current electrical impulses which pass over one and the same line, and actuate a set of relays, each impulse in the group affecting the operation oi' a particular relay, by a 1922. Serial lilo. 577,649.

method described below. These relaysactu- I ate rmagnets which set .up combinations of Vletters and (5 others concerned in certain functions of the printer, such as carriage return, figure shift, and soon. lThe signals for message characters as commonly used in these systems, constitute'what is usually termed a live-unit code, that is, it consists of permutations of two elements taken ve at a time. In one system of operation these two elements may be positive and negative potentials,inwhich case the code signal for a character consists ol' the distribution through' timeV of ve 'elements composed of positive and negative impulses. Inanother systemo'lZ operation the two elements may consist of a time-interval when an impulse is sent, and a time-interval when no impulse is sent, this being the methodrot closed and open circuit operation. i The code signal for the letter A, for example, is which in theV positive and negative system ot operation means that the first and second' units of the signal are positive impulses, the third, four-th, and lifth, are negative im-f pulses. In the open and closed circuit system of operation, this code signal means that only 'the first two time units are occupied' by the passage ol current, the last three, unoccupied. The perniutations of trai'ismitted impulses are governed by a set of make and break keys operated :it the transmitting end manually, by means ot a sending keyboard similar in l'orm to the ordinary typewriter keyboard, or automatically by means of a transmitter controlled by aperforated tape.

In order that a plurality of relays shall lbe controlled by impulses of equal potential, and all coming over the sameline, or through the same channel, and that the permutation of relays actuated at the distant end shall correspond to the permutation ot depressed keys at the sending'end, in the heretofore prevalent'systems, connection is momentarily established between each key at the sending end and its corresponding re- 'lay at they receiving end and the live temporary connections between the rive pairs of keys and relays are established in a fixed sequence, one after the other. Thus, for example, in the case out five relays .respeclli) tively controlled by live make and break keys, the time necessary to send the signals for one message character or letter is divided up into tive equal intervals; during the first interval key lat the sending end is co-nnected with its corresponding, relay 1A at the receiving end; during the second interval, key 2 at the sendingend. is con.- nected with its corresponding relay 2 at the receiving end, and soV on; The method of eiiectin such a correspondence in action by.

transmiting similar impulses through one and the same channel involves the use of a distributor and. various other apparatus in` eluded under the general term synchroniz ing mechanism.

The principle ot the synchronizing distributcr is this: Twosimilar rings, one on the sending face of a distributor at the transmitting station, the other on the receivinfA 'lace of an identical distributor at the receiving. station, are each divided into at least i'ive equal segments. A pair of rotating brushes on these distributors are connected to the line, and when these brushes revolve they sweep over and make contact,

yresponding segments ci the receiving distribut-or, the interval of each connection being the time of one-fifth of a revolution of the rotating brushes. rllhus, 'eachV message character is transmittedas a combina` tion of live separate or discrete impulses distributed equally7l and in a definite sequence through an interval ottime, and 'tor each revolution of the brushes, the code impulse combinations forone and only one character or letter. are transmitted and re.- ceived. The synchronization lof the two distributors so that the respective brushes revolve with exactly the same angular velocityis a. very complex feature` of these printing telegraph systems, and acts as a.

limiting factor upon the speed of operation.V

inv my system no such synchronization is necessary, 'for all of the signals comprisingv the combination ofV impulses for av single character are transmitted simultaneonsly, and at the receiving end are properly isolated by tive selectively tuned circuits.

In order that the invention and its inode.,

et application maybe readily"understood by persons skilled in the art, I have, in. the

accompanying illustrative drawings, and in the detailed` following description. based thereon, set kforthy an embodiment of'the same.

Figure l is a diagrammatic sketch ot one Yform of arrangement ofy circuits whereby each of a plurality of high frequency alter'- nating currents may be modulated or nonmodulated in. permutations corresponding to code signals for message characters, the modulated'currents impressed upon a line, andthe modulations isolated at the receiving endv by a plurality of selectively tuned circuits.

Figure 2' is a diagrammatic sketch of one form'of arrangement or" circuits whereby a plurality of complete sets o modulated alternating currents lare simultaneously impressed upon a line, the members of each set being isolatedv at. the receiving end by a plurality ot' selectively tuned circuits, thus eifecting. multiplex operation.

Figure 3 is a diagrammatic sketch of an arrangement of circuits for the simultaneous operation ot' transmitting andy receiving sets Vat the same end of the line so that stations may transmit and receive messages at the same time-at both ends of t-he line.

Figure 4 is similar'to Figure l, except that the arrangements in the former are adapted for communicationl by radio.

Having more particular reference to the drawings and in connection with which like characters of reference designate similar parts tl'iroughout, in Figure 1, A, B, C, D, andE, are sources of high frequency alternating current of different frequencies. called hereafter. carrier waves which is modulated telegrapliically, by means now welleknown in the art through `the imposition oftmodulating frequency by modulators F, Gr, H, I, andJ, respectively, when keys K, L, M. N, and O are operated.

'Q is a sending keyboard of well known term, or an automatic tape-controlled transmitter, also of well known form, which governs the action o't'the keys l( to Opin a permutative manner according the thel combinations of the code signals representing niessage characters.

Let us suppose,'tor purposes of illustration, that A is asourceo'f carrier wave cureachr of a i tu rent ofV a trequencyv of 20000 cycles per second; B isa source of carrier wave currentof afrequency of 80000 cycles pei' second, and soon, up to E, which is a source of carrier wavey currentl of a frequency of 60000 cycles per second. F modulates carrier wave A by 1000.v cyclcspcr second when keyy K is closed; similarly G, H, I, and J modulate the carrier waves B, C, D, and E, respectively by 1000 cycles per second, when keys L, M, N, andV O, respectively, are closed. The modulated carrier waves are impressediupon the lines U and U, which at thevreceiving end branch off into the live seh'rctively tuned circuits A to E', each of which is responsive only to a certain predetermined frequency. Foi' example, in my illustration, A is a circuit responsive to a carrier wave current of a frequency of 20000 cycles per second, and no other; B is responsive only to a carrier wave current of a frequency of 30000 cycles per second, and so on, up to E', which is responsive only to a carrier Wave current of a frequency of 00000 cycles per second.

F is a circuit for rectifyingthe high frequency current received by A, and thus converts the high frequencyV current into a loiv frequency current which is the modulating frequency, and then this current passes on to relay LK, tuned to respond to the modulating frequency imposed on the carrier Wave A by modulator F. Current will flow through F, for example, only when key K is closed, or, in other'ivords, when carrier wave A has been modulated by F. lVhen this key is open, no current ivill flow through F, thus leaving relay K in-k operative. Gr, H', I, and J are similar circuits, adjusted in the same ivay as F for rectifying the high frequency currents received by B', CD, and E respectively, and

thus keys L to O and circuits G to J con-V trol tlie operation of relays L to O', respectively inthe same manner as key K and circuit F control relay K. Relays K to O are operatively connected to R, ,which is a printing mechanism of Well known form, and is controlled by the permutatively energized and unenergized conditions ofthese relays so that it prints or records the message characters transmitted from the sending sta,- tion.

Let us suppose that it is desired totrans-y init the signals foi the letter Z the code combination for which is represented by the symbols `-[----l. This means that relays K and O are to be energized, the others are to remain unenergized. The key Z on the `manually operated keyboard, Q, is depressed, or an automatic tape-con` trolled transmitter functions, to cause keys K and O to be closed simultaneously, thus causing the modulators F and J respective` ly to modulate the carrier Waves from A and E, respectively, but leaving the carrier Waves from B, C, and D, unmodulated. In my il.-Y

lustration, lines U and VU will be simultaneously traversed by Waves of the following frequencies: 19000-21000, 30000, L10000,

50000, andV 59000-61000 cycles per second,Y

At the receiving end circuits F and J Will be the only ones that will allovv currentto reach the rela-ys, for circuits G', H and I ivilljust neutralize the unmodulated carrier waves from G, H, and I, respectively, and therefore only relays K and O Will be energized. This action corresponds there fore to the permutation of closed keys at the transmitting end. 'It `is thus seen that although the five relays K" to O are all operated by currents simultaneously traversing the line U'U,the operation of any one of the live relays is independent of and will not be interfered Withby the operation of any other of the five relays., The heterogoiious combination of modulated carrier waves is broken up into the homogenous elements of individual impulses in a permutation corresponding to the' proper code signal for the character transmitted. It is apparent, furthermore, that in this system not only is the time necessary to transmit a single character `reduced to one-fifth of the time re quired in thelieretofore prevalent systems...V

but also the speed of the transmission and reception can be materially increased be-1 cause no limiting speed of operation is iiitroduced in this method by any synchronizing devices. f

It is obvious that the system vhere pro- X are their corresponding receiving sets,

each of which is similar in construction and operation tothe single receiving set, P of Figure 1. It isto'` be understoodthat WV vand, lV of F igureQ comprise all the elements included iirP and P', respectively of Figure It is of course u all of the transmitting sets-be located at one unecessary that Y end of the line, and all ofthe receiving sets' 4 at the other end of theV line, and in fact thiskwould not be the practical method of operation. A :plurality of transmitting sets and a plurality of receiving sets may co-exist at both ends of the line 'with no interference whatever, so long as proper frequencies are selected for the operation of each corre-` spending transmitting andl receiving set. This is shown in Figure 3 Where A and B represent complete transmitting sets comprising all the elements included by transmitting set P ofFigure 1, Band B represent complete receiving sets comprising all the elements included by receiving set P of Figure l, Transmitting set A controls receiving set A and transmitting set B controls receiving set B', but transmitting set Ay and receiving setB are located atl one end of the line, While transmitting set B and receiving set A are located at the other end of the line.

lVhile l have shown the transmitting sets bridgedy across the lines U and U, I do not Wish to restrict myselt to this method o'l.

connections, for the modulated carrier waives `may pist as feasibly be inserted.. directly inl series with the line circuit. y

and J, it is, oi course, quite possible to have asingleymodulatingelement suitably coniiected tothe keys K', L, M, N, ands O, so that the modulation may be imposed! upon. any of the carrier Waves..

, Furthermore, the generators herey described' have a single period, but multi-peiiod generators may be used, in Which ease the individual frequencies would be used in. the separate transmitter circuits.

It is to be understood that either a two- Wire complete metallic circuit, ory a single Wire ground. return circuit is possible. In the drawings, the former method-is shown.

lliile have illustrated my invention as utilizingv a code consisting oi.l tive elements, it is obvious that a code ot' a greater numberV oi elements may. just as easily be used,

depending upon .the printing mechanism that is employed, and I therefore do not wishA to limit myself toa code consisting ot any particular number of elements.

.lit isV also obvious that instead of using a lineupon; which. the modulated carrier Waves arev impressed,` the modulated carrier Waves may be of radio-frequencies `and radiated inte space by means oian. antenna or any other vsuitable radiating device. This is shown inf Figure 4in which an antenna Q, with; its. ground, Rf, serves toradiate the waves into space andat'the receiving` stationa eoi'respnndingl antenna Q5, with its ground', R", serves to` receive the radiated Waves. In this ligure lil and lV represent all the elements included' undeil) and P',-

rcs'pectively, in- Figure l. rl=`lie method of. employing modulated different .frequency carrier waves to eliminate'the necessity Voit synchronizing mechanisms cani also be applied to systems other than` printing tele.

graphs, andA it is iiiteudedathat this feature be included among the othersgof my invention.`

In tact, several modifications of: the systeni are possible Without departing from the spirit ot the invention or the scope of .the claims. Y l

That I claim as my invention is the following:

la. In a lprinting telegraph system,` the combinationot a set of generators of radiofrequency oscillations yof different radiofrequencies, means tor telegraphically modulating saidoscillations by a. single modulating irequency, a set ot make and break keys .respectively controlling the `oiY saidisolated' oscillations, each of said last-named means being associated with and controlling a relay which is energized when said modulation is present, but is unenergized when said modulation is absent, andl ak .printing or recording mechanism con-,-

trolled bythe permutative operation of said energized and unenergized relays.

2.' In a multiplex printing telegraph system, the combination oa plurality o'tgen- Vcraters of radio-frequency oscillations of di-iiei'ent radio frequencies, means for tele- .graphically modulating said. oscillations in veach set by a single modulating frequency,

a plurality ot sets ot make and break keys respectively controlling they modulation or non-modulation oscillations. by said modulating frequency, means .for operating said sets of keys simultaneously and'` permuta.-

tively, to. correspond tol the permutations ot.

a pluraltuniti signaling code representing.k

message characters, ineansor radiating said sets of; permutations of modulated and'non-v modulated oscillations into space simultaneously., afpluralityy ofi sets of receiving instruments ltuned to; receive andv toi isolate said radiated sets ofoscillations, ineansiorI detect-ing the presence or. absence oi' modulation in each. of'. said isolated oscillationsl 'in each o'tsaid'sets oii oscillations, each of saidilast-nained; means beingA associated with and controlling a: relay which isr energized Whenssaid modulatioit is present,V but is unencigizedwhen said; modulation is absent, and a plurality of printing or recording Amechanisms individually. controlled by the perinutative operation of suitable groupings of said relays into operative sets.,

3; In. a system of multiplex printing telegrapliy', the combination of: an antenna,

Va set of transmitters. and a. set oi' receivers electrically: associated. with' said antenna, said. transmittersgenerating. radio-frequeiicy. oscillations or different frequencies, and said set of.' receivers being adjustedf to' -be separately in resonance for frequencies corresponding to those generated by the transmitters at, some other station from which signals are received, means for telegraphically modulating saidr oscillations in each of said transmitters by a single modulating frequency, a set of make and break keys associated with each of said sets of transmitters, eacli of said set of keys respectively controlling the modulation or non-modulation of the oscillations of the set of transmitters with which set of keys is associated, means for operating each of said set ot keys simultaneously and permutatively to correspond to the permutations of a plural-unit signaling code representing message characters, means, associated with each of said receivers, for detecting,` the presence or absence of modulation in the oscillations received by each of said receivers, eacli of said last-named means being associatedrwitli and 'controlling a relay which is energized when said modulation is present, but is unenergized When said modulation is absent, and a printingr or recording mechanism, said mechanism being controlled by the permutative operation of said energized and unenergized relays.l

fl. The method of radio-telegrapliically effecting a correspondence and sin'iultaneity of action between the elements of a set of controlling electrical instruments and the corresponding elements of one or more sets of controlled electrical instruments, by means of a plurality `ot carrier Waves of dierent frequencies, said carrier Waves being permutatively modulated or non-modulated by a modulating frequency'according as the respective elements of said set of controlling instruments are-operated permutatively, the several carrier waves being isolated individually at the controlled stations by selectively tuned circuits associated With said sets'of controlled instruments, the presence or absence of said modulating frequency in said isolated carrier Waves respectively causing` the elements of said set ot controlled instruments to be actuated or non-actuated as the case may be.

VIn testimony whereof I ailix my signature.

WILLIAM F. FREDMAN. 

